Express your answer as a mixed number simplified to lowest terms. $11\dfrac{9}{15}+7\dfrac{5}{15} = {?}$
Separate the whole numbers from the fractional parts: $= {11} + {\dfrac{9}{15}} + {7} + {\dfrac{5}{15}}$ Bring the whole numbers together and the fractions together: $= {11} + {7} + {\dfrac{9}{15}} + {\dfrac{5}{15}}$ Add the whole numbers: $=18 + {\dfrac{9}{15}} + {\dfrac{5}{15}}$ Add the fractions: $= 18+\dfrac{14}{15}$ Combine the whole and fractional parts into a mixed number: $= 18\dfrac{14}{15}$